The present invention relates to a novel brace mechanism which is especially adaptable to bracing the knee joint.
Knee braces have been employed to support the knee of a patient after knee surgery or subsequent to a fracture of the tibia or femur. Recently it has been found that the use of a knee brace which allows limited rotation of the knee reduces joint stiffness and atrophy of the muscles of the leg surrounding the knee joint. It has long been recognized, that the knee joint is a polycentric system i.e. the knee pivots on more than one pivot axis during movement from flexion to extension.
Reference is made to U.S. Pat. No. 4,523,585 showing a four bar linkage mechanism which achieves a polycentric motion that generally follows the actual motion of the human knee. Among the recently recognized movements of the human knee is the translational motion, or "drawer", between the tibia and femur. Reference is made to U.S. Pat. No. 4,961,416 which devised a unique bar apparatus to limit such translational motion during extension of a braced knee.
Although the brace device described in U.S. Pat. No. 4,961,416 successfully controlled translation or "drawer", it has been recently hypothesized that the medial portion of the knee translates differently than the lateral portion of the knee. For example, it is believed that the medial portion of the knee may translate on the average of 8 mm while the lateral portion of the knee may translate up to 20 mm. Thus, it is important to incorporate such differential translation into a knee brace in order to closely follow the natural kinematic motion of the knee.
U.S. Pat. Nos. 4,723,539 and 4,773,404 illustrate a linkage which permits sliding rotation between the femur and tibia by the use of cam slots and cam pin followers. Such linkage is subject to constant friction and wear, and generates excessive noice during movement.
A brace which solves the problems found in the prior art would be a great advance in the orthopedic field of medicine.